At Groom Lake throughout the 1960s, Annie Jacobsen explains (in Area 51), at least once a month and always before dawn, base personnel would be shaken from their beds by a violent explosion:
When the rumbling first started happening, Ken Collins would leap from bed as a sensation that felt like a massive earthquake rolled by. A nuclear bomb was being exploded next door, underground, just a few miles west of Oxcart pilots’ quarters. Next, the blast wave would hit Collins’s Quonset hut and then roll on, heading across the Emigrant Mountain Range with a surreal and unnatural force that made the coyotes wail.
Early one morning, Collins woke not to a boom but to banging on his door:
Collins followed [Colonel] Slater in a run toward the hangar where the Oxcart lived. There he was quickly briefed on the situation: the Pentagon had called to say that a Russian reconnaissance balloon was flying across the United States, floating with the prevailing winds in a westerly direction. Collins was to find the Soviet balloon—fast. Normally, the flight surgeon would have spent two hours just getting Collins into his pressure suit. That morning Collins was suited up and sitting in the cockpit of the Oxcart in a little over thirty minutes. Up he went, blasting off the tarmac, north then east, on direct orders by the Pentagon to “hunt and find” the Soviet weather balloon visually and using radar.
Up in the air it dawned on Collins what a wild-goose chase he was on. What would a Russian reconnaissance balloon look like? What were the chances of making visual contact with such a thing? At speeds of more than 2,200 mph, he was traveling more than half a mile each second. Even if he saw the balloon, in just a fraction of a second it would be behind him. Even worse, what if he actually did get that close to the flying object? If the Oxcart hit anything while moving at Mach 3, the plane would break apart instantly and he’d be toast.
Flying somewhere over the middle of the continent, Collins briefly identified an object on radar about 350 miles away. As instructed, he flew around the object in the tightest circle he could perform at Mach 3, which meant his circle had a radius of about 400 miles. He never saw the balloon with his own eyes.
After Collins returned to base, engineers scrambled to read the information on the data recorder. The incident has never been declassified. Admitting that the Soviets invaded U.S. airspace—whether in a craft or by balloon—is not something any U.S. official has ever done. Collins never asked any follow-up questions. That’s how it was to be a pilot: the less you knew, the better. He knew too many fellow pilots from Korea who had come home from POW camps missing fingernails—if they came home at all. Now, ten years later, pilots shot down over North Vietnam were experiencing the same kinds of torture, maybe worse. The less you knew, the better. That was the pilots’ creed.
Did we have any other response at the time? Not sure we had the capability to track and shoot down.
Was this even useful to the Sovs? Other than the eye-poking aspect. I don’t think there was real time data collection; whoever would have to recover the balloon for the info; likely a long shot endeavor.